The regulation of water and electrolyte metabolism is dependent in large part upon vasopressin (ADH, antidiuretic hormone), the renin-angiotensin-aldosterone system, and, possibly a humoral natriuretic factor. The primary objective of this research proposal, as well as the applicant's long-term research goal, is to delineate the role of ADH in this regulatory process. To achieve this goal, I shall focus upon the following: a more complete characterization of the cardiac and arterial receptors which serve as volume receptors in the control of ADH secretion; the interplay between the cardiac and arterial receptors in the control of ADH release; the integration of the several hormonal systems which regulate the volume and the composition of the body fluids, and the further integration of these systems with the system responsible for cardiovascular regulation; a more complete characterization of the processes responsible for the removal of ADH from the circulation, with emphasis on an attempt to determine the extent to which these processes are under physiological control. Finally, development of a radioimmunoassay for ADH will be attempted.